Cryptoperlan stoneflies inhabit the headwaters or upper stream areas of rivers. A molecular phylogeographic study of cryptoperlans in the Japanese archipelago and on Taiwan Island has been conducted. Altogether the mtDNA 16S rRNA region of 71 individuals from 61 populations, the mtDNA COI region of 76 individuals from 41 populations, and the nDNA Histone 3 region of 56 individuals from 52 populations were sequenced and analyzed. The respective ML, NJ, MP and Bayesian dendrograms were proposed from the sequencing data for the 16S rRNA region (362-bp), the COI region (540-bp), and the Histone 3 region (322-bp), estimated using Yoraperla uenoi as an outgroup. Based upon those data and the resulting dendrograms, it has become clear that the cryptoperlan stoneflies of the Japanese archipelago and those of Taiwan Island comprise two major clades. The first of these two major clades consists of a number of OTUs [operational taxonomic units: Cryptoperla japonica (Honshu, Shikoku and Kyushu Islands) + C. ishigakiensis (Ishigaki-jima Island) + Cryptoperla spp. (Okinawa-jima and Taiwan Islands)]. The other clade consists of the species Cryptoperla kawasawai inhabiting only Shikoku Island. Of particular note, C. kawasawai was observed to be significantly genetically differentiated from all other cryptoperlans examined. Yet, despite the fact that the specimens of C. japonica were taken from a very broad range of populations, their genetic diversity was relatively low, similar to that of C. kawasawai, which inhabits only a limited region within Shikoku Island. Furthermore, even the species C. kawasawai was revealed to be composed of two significantly genetically differentiated subclades. It is considered that this genetic structure among cryptoperlans largely reflects the geological history from the middle to upper Miocene Epoch (i.e., Tortonian stage) of the Japanese archipelago and Taiwan Island.

Biomanipulation has been employed in numerous locations throughout the world as a means for reducing phytoplankton biomass; however, it has not been employed very often in Japan. A common approach involves the introduction of piscivorous fish to reduce the abundance of planktivorous fish. In our study, to first apply biomanipulation, we stocked Lake Shirakaba (a high-altitude, protected area in a park) in central Japan with rainbow trout fingerlings and cladoceran Daphnia (Daphnia galeata) in 2000. A “pre-biomanipulation” data set (1997–1999) and “a post-biomanipulation” data set (2000–2006) allowed us to evaluate the lake's response to biomanipulation. After the biomanipulation, zoo-planktivorous pond smelt disappeared and a large population of Daphnia had been established, which substantially reduced the number of the previously dominant small cladocerans and rotifers. Water transparency increased from about 2 m (before biomanipulation) to more than 4 m (after biomanipulation). Reductions in algal biomass and increased transparency led to expansion of the submerged macrophyte Elodea nuttallii. Total phosphorus concentrations declined as well over this time period. Based on these results, we concluded that biomanipulation using piscivore and Daphnia stocking succeeded in improving lake water quality by reducing algal abundance and providing favorable conditions for the establishment of rooted plants.